Modern manufacturing operations and other operating devices use many types of equipment that are subjected to loads that cause heating in portions of the particular machine or unit. Sometimes the heating occurs in electrically powered equipment, such as electric motors, welding transformers, and welding guns. The heating may also occur in equipment such as gear boxes and machining equipment that experience frictional loading. Often the equipment is used in circumstances that make maximum use of its design capabilities and may result in substantial heat generation within a particular heavily loaded, manufacturing unit. Further, the equipment may be expected to operate with minimal operator attention or oversight.
Thus, there is a need for inexpensive and low energy-consuming devices that may be adapted to function autonomously as a temperature monitor, providing an overheat signal or over-temperature signal, for the particular environment of many different machines used in manufacturing or other operations. There is a need for such devices to fit, non-obtrusively, on or in thermal contact with the equipment, or within the equipment, and to give a visible warning signal if, or when, some portion of the equipment reaches a temperature that indicates that it is overheating, which is likely to be harmful to its continued operation.